Radar transmit receive switch



July 16, 1957 310 131 2,799,804

RADAR TRANSMIT RECEIVE SWITCH Filed Oct. 21, 1952 WITNESSES: v INVENTOR 82,4 L A? I Manfred A. Biondi BY M 0 5 5M ATTORNEY United States Patent 6 RADAR TRANSMIT RECEIVE SWITCH Manfred A. Biondi, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a cerporatlon of Pennsylvania Application October 21, 1952, Serial No. 315,41

11 Claims. (Cl. 315-41) My invention relates to gas-filled electrical discharge devices and in particular comprises a novel gas-filled transmit-receive switch, hereafter referred to as a T-R switch, used for automatically connecting components, such as a radar receiver, into and out of certain high frequency electric circuits.

T-R switches have been widely used in radar circuits to permit a sensitive receiver of ultra short-wave signals to remain operatively connected to the antenna of a radar set to respond to incoming signals of low power except when the transmitter connected to the same antenna is supplying a pulse of enormously greater power. At the instant such a pulse appears at the point where the receiver is connected to the antenna, the T-R switch functions to short-circuit the receiver, by passing the pulse to the antenna and saving the receiver from the ruinous influx of energy which it would otherwise suffer.

To effect the above purpose, the T-R switch must change with great rapidity from a nearly non-conductive to a sufficiently conductive state when the pulse wavefront appears, and must change back again to the nonconductive condition with great rapidity when the pulse has passed.

One widely used form of T-R switch comprises a chamber containing a substantial quantity of a gas surrounding a pair of electrodes which are respectively connected across the channel leading electric pulses to the receiver inside a chamber which forms a cavity resonator. An ancillary chamber contains an auxiliary keep-alive electrode which maintains an electric discharge of low current density serving to supply a certain degree of ionization in low concentration to the gaseous atmosphere between the main electrodes. The U. S. Patent 2,525,468 to Daniel Alpert describes and claims such a TR switch.

To effectively perform the above-described functions, it is necessary that the gas between the electrodes shall rapidly increase in ionization under a relatively moderate voltage-rise between the main electrodes, i. e. it should have a comparatively low break-down voltage; and it should deionize rapidly when the voltage is removed.

One object of my invention is accordingly to provide a novel T-R switch which shall have a low recovery (i. e. deionization) time.

Another object is to provide a novel T-R switch having a relatively moderate ignition (i. e. breakdown) voltage.

Still another object is to provide a gaseous atmosphere for electrical discharge devices which shall ionize and deionize with great rapidity.

Still another object is to provide a novel atmosphere for electrical discharge paths.

Other objects will become apparent upon reading the following description taken in connection with the drawings, in which:

Figure l is an elevational view in section of a cylindrical form of T-R switch in accordance with my invention; and,

2,799,801 Patented July 16, 1957 Fig. 2 is a perspective view of a rectangular form of T-R switch and may be utilized advantageously as a pre- T-R switch.

Referring in detail to Fig. 1, the latter shows a section, on a plane through its central axis, of a chamber 1 which may be of any suitable metal such as brass or copper having a pair of windows 3 and 4 of glass connected to the metal by suitable rings 5, 6 which may consist of the iron, nickel, cobalt alloy described in Scott Patent 2,062,335. A projection 7 on the wall of chamber 1 coacts with another projection 8 on the opposite wall to form a discharge gap. The projection 8 is hollow and in its axis is positioned an electrode 9 insulated from the walls of container 1 by a glass sealing member 11. In use, as an electrical gradient exists between electrode 9 and projection 8 when the chamber 1 resonates, an electrical discharge is maintained between the electrode 9 and projection 8 from which gaseous ions migrate into the gap between projections 7 and 8.

The container 1 contains an atmosphere of helium gas admixed with iodine vapor; for example, I have found helium at a partial pressure of about 30 mm. of mercury admixed with iodine at a partial pressure of 1 mm. of mercury to be satisfactory for many purposes, both pressures being given for thirty-five degrees centigrade. Under this condition there will be thirty helium molecules present for each iodine molecule.

In use the T-R switch of Fig. l is inserted in a wave guide so that the electric waves flow into it through one of the glass windows 3, 4 and out through the other. When the electromagnetic field is of the low intensity characteristic of received signals coming from the antenna, the chamber 1 merely acts as a resonator, permitting the waves to flow through it to the receiver proper. When, on the other hand, the local transmitter sends out a pulse, the electric field in the chamber 1 rises to such an intensity as to produce a breakdown in the gas between projections '7 and 8 which short-circuits the wave guide and prevents transmittal of electric fields of harmful intensity through the outlet guide to the receiver.

Fig. 2 shows a rectangular type of T-R switch which has been found particularly useful as a pre-T-R switch, that is a resonant chamber inserted in the wave guide between the TR switch and the antenna, and functioning as a TR switch to short-circuit the line and reflect the greater part of the energy from a transmitter pulse before it reaches the TR switch proper. If waves of intensity likely to be harmful to the receiver manage to pass the pre-T-R switch, the main TR switch arcs over and reflects them as described in discussing Fig. 1.

Fig. 2 may comprise a simple box 21 of brass or copper having windows 22 and 23 in opposite sides made as described in connection with the windows of Fig. 1. In Fig. 2, there are no specific arc-over projections like projections 7, 8 in Fig. 1, but, as the opposite edges of the window 22 or 23 have different electrical potential when the resonant chamber resonates, arc-over occurs between the opposite edges of window 22 or 23 when the electric field intensity of waves flowing in from wave guides covering these windows attains a dangerous intensity.

A filling of the same gaseous mixture described in connection with Fig. l, and of the same pressure, is suitable for most purposes in using the T-R box of Fig. 2.

Vlhile l have described the gaseous filling of the T-R boxes in Figs. 1 and 2 as partial pressures of helium 30 mm. and iodine 1 mm. of mercury, hydrogen may be substituted for helium where rapid suppression of ionization in the gas is paramount even though attained at the expense of higher ignition voltage. Atmospheres in which either hydrogen or helium are present at partial pressures between 10 and mm. of mercury with chlorine,

.bromium, iodine, or sulphur hexafllloride (SE6) present at partial pressures from 1 to mm. of mercury are useful. The higher the pressure the shorter will be the recovery time, .i. e., the peiod required to'suppress ionization to aspecified value, :but the higher will be: theiignitionnzoltage required to cause breakdown across the electrodes of .thezswitch. Thesgases listedior thej lower-pressure :component in he. mix ure are leotronc'gative gases.

Ielaim asmy invention:

51. A .-'1".R switch comprising an envelope having'v'va-lls o sonduc inamat rial t rm ng a avity re r. a P :QfgOPPQSBQ conductors'fprm-ing a'disch-arge gap between points of .diiierent electrical potential -when said cavity resonatorzresonates, and agaseons atmosphere consisting .qfihelium "admixed withaiodine in said resonator.

g2. T-gR switch comprising an envelope having walls of conducting material forming a cavity resonator, apair otopposed conductors forming a' discharge-gap between points of ,difierent electricalpotential when said cavity resonator resonates, and a gaseous. atmosphereconsisting of :helium admixed with iodine in said resonator, the number of helium molecules being aboutthirty times ,the number of iodine molecules.

'3, A T-R switch comprisinganenvelope having walls of conducting material forming a cavity resonatonapair of opposed conductors forming a discharge; gap between points of different electricalpotential when said cavity resonator resonates, and agaseous atmosphere consisting of helium admixed with iodine in .said resonator, said atmosphere having a total pressure of about thirty mm. of m ury '4. .A TR switch comprising an envelope having walls of conducting material forming a cavity resonator, a pair of opposed conductors forming -a discharge ,gap between points of different electrical potential when said cavity resonator'resonates, and a gaseous atmosphere consisting of helium -admixed with iodine in said resonator, said atmosphere having a pressure of about thirty "mm. of mercury and the number of helium molecules being'about thirty times 'the number of iodine molecules.

=5. ;An envelope of conducting material forming acavi-t-y resonator, a gap within said resonator having its termini at pointsbetween-which an electrical gradient exists When said cavity resonates, and an atmosphere said envelope 'consistingof helium admixed with iodine. 4 V

"6. An envelope of conducting material forming-a-cavity resonator, a gap within said resonator having its termini at points between which an electrical gradient exists when 4 said cavity resonates, and an atmosphere within .said envelope consisting of helium admixed with iodine, about thirty times as many helium molecules as iodine molecules being present.

7. An envelope of conducting material forming a cavity resonator, a gap within said resonator having its termini at points between which an electrical gradient exists when said cavity resonates, and an atmosphere :within said envelope consisting of helium admixed with iodine, .said

atmosphere having a pressure ,ofabout mm. of

mercury. V

8. A11 envelope of conducting material forming a cavity resonator, a gap :within said resonator having itstermini at points between which .an-electric al gradient exists when said cavity resonates, and an atmosphere within said envelope consisting of helium admixed with iodine, said atmosphere having a pressure of about thirty mm. of mercury and comprising about thirty times as many e iu molecules as iodine molecules. a

9. An electrical discharge ienvelope uenclosing a pair of discharge electrodes andenclosing aniatmosphere-of helium admixed withiodine, there :abeing sab out thirty helium molecules foreach iodine molecule.

1-0. An'electrical discharge :envelope' enclosing apair of dischargeelectrodes and ,enclosingranratmosphere of helium admixed with abolltthree percentgby partial pressure of iodine, said =atmosphere,haYing-apressure of about thirty of mercury, about thirty helium molecules being present foreach iodine molecule. V 11. A T-R switchcomprising an envelope-enclosingza pairof electrodes inqan atmosphere consisting of gas atga partial pressureof 10 to 1.9.0 mm. of mercurfy drawn from the group .which consists of helium and hydrogenand gas 'at a partial pressure of 1 to ;1.0 of mercury drawn from the group which consists of chlorine, bromine, iodine. and sulphur hexafluoride.

References Cited in the file ,of this patent UNITED STATES PATENTS 

